1. Technical Field
The present invention relates generally to the construction of concrete structures, and more particularly to the construction of those structures using concrete molding blocks.
2. Background Art
The construction of concrete structures such as building foundations and walls was traditionally accomplished using removable forms into which uncured concrete is poured, or by the laying and mortaring together, in brick-like fashion, a series of cement blocks. These methods require the hard to master skills of an experienced professional. This is one factor causing construction by these methods to be expensive.
In the building of a structure using concrete forms, the structure is made by assembling a series of braced wood or metal walls in the desired shape of the finished wall, foundation, etc. Once the concrete has been poured into the forms and cured, the forms must be removed, cleaned, and repaired prior to transporting them away from the construction site. As can be imagined, not only does this system require skilled workers to assemble to forms properly, but it is also costly in terms of the time consumed to set-up and disposition the concrete forms. On top of all that, add the expense of transportation and storage. The form sections have to be shipped to the construction site and then stored prior to assembly. The sections being made of wood or metal are too heavy to be lifted by hand, so the use of a forklift or crane is required to remove them from the delivery trucks or to bring them from on-site storage to the location where the concrete structure is to be built. Typically, the number of forms required and their size dictates that more than one truck be used to bring them to the work site. Additionally, to incorporate structural features, such as windows, electrical outlets, wiring, plumbing, and the like the forms have to be cut. As the structural features of a building are usually unique to that building, the modified form can not be used for future construction jobs, except possibly as scrap that can be further modified to fit some structural feature of that job. And, once the forms have been removed, the concrete is exposed to the elements. This can require the installation of insulating materials to satisfactorily maintain the temperature of the interior of the structure. Also, the exposed concrete is susceptible to cracking which can cause water and air leaks into the structure. And finally, the removed forms have to be cleaned, restored, and eventually shipped out of the construction site.
Cement block construction methods present problems similar to concrete forms and a few disadvantages of their own. The blocks are stacked like bricks and mortared together. The mortar joints are susceptible to cracking and so subject to air and water intrusion just like the formed concrete structures. In addition, the strength of a cement block structure is less than that of an all concrete equivalent because of the mortar joints and more susceptible to failure. The sight of a cement block wall cracked and crumbling along its mortar joints is not uncommon. Cement blocks structures are also poor insulators, so may require the addition of insulation to efficiently maintain the temperature of the interior of the building. Once stacked, the cement blocks must be cut to provide for the installation of electrical outlets, plumbing fixtures, and the like. This can only be accomplished with considerable difficulty as the cement must be sawed through to create the necessary openings. The cement blocks are bulky and heavy. Therefore, several trucks may be required to transport them to the construction site, and once there, any movement of more than one or two individual blocks must be accomplished with the use of a forklift or crane. And, just as in the case of the concrete forms, the blocks would require on-site storage since it can take several days to complete a cement block structure. Although no removal and form cleaning is required as with concrete forms, there is still some cleaning associated with cement block construction methods. As stated, it can take several days to construct a cement block structure. After each day, the unfinished ends of a the cement blocks must be carefully cleaned of excess mortar, as it will harden overnight thereby interfering with the lying of additional blocks the next day. Also, once construction begins, the shape of the structure can not be rearranged without demolishing the already laid and mortared blocks. Therefore, little flexibility exists in this construction method. And, finally, the level of skill required to construct a cement block wall is even higher than with one made with concrete forms. Accordingly, the labor costs can be even higher.
Recently, styrofoam molding blocks have been introduced as an alternative method of constructing concrete structures. Typically, these hollow blocks are stacked in a brick-like fashion similar to the cement blocks. However, they are not mortared together. Instead, concrete is poured into the hollow centers of the blocks. Usually, the styrofoam exterior is left in place. Although, these type of blocks offer some advantages over the concrete forms and cement block construction methods, they present disadvantages as well. They are not heavy, but they are still bulky. This means that several trucks are still required to transport sufficient quantities of the blocks to the construction site. The fact that the blocks are made of styrofoam or some other plastic foam material creates several problems related to their strength. First, they are easily damaged during transport and handling. Therefore, the number of unusable blocks can be high. These type of blocks usually have integrally formed interconnections. However, these interconnections are typically not strong enough to support the structure once the concrete is poured in, therefore, the structure must be braced prior to the pouring. Additionally, the foam materials used to make the blocks have almost no shear strength. Accordingly, they provide no resistance to cracking of the concrete. This lack of resistance follows from the fact that a crack in concrete only propagates if its point of origin on the surface can widen. The foam offers no resistance to this widening as the material shears easily. Also, to provide enough strength not to burst under the force put on the foam block by the uncured concrete poured inside, the foam must be somewhat thick. Typically, the walls of the block can be two inches thick or more. This presents some unique problems. The sections of the structure that form the perimeter of features such as windows and doors necessarily have two inches of foam material between the concrete inside the block and the door or window frame. Someone could chisel through the foam without much difficulty and access the interior of the structure. With such a hole, a door or window could be unlocked and the structure burglarized. The thickness of the foam also makes attachment of facing materials difficult. Any panel-like facing must be attached to studs or the like which have been pre-positioned in the concrete and which are long enough to extend through the foam, or must be pounded into the concrete while leaving at least two inches of the stud's shaft protruding through the foam. As can be imagined the shaft of such a stud would have to be unusually thick to allow the cantilevering of a facing panel two inches away from its anchoring point. The other alternative would be to glue the facing panel to the foam surface. However, this would provide little structural strength. The panel could literally be pulled free taking a portion of the foam with it. Such a method would be particularly unsuitable for exterior facings, or heavy facing materials such as brick of rock. And for plaster type facings, such as stucco, a backing board would have to be installed by one of the above mentioned methods before it could be applied. The thickness of the foam also makes the doubling of the blocks to create a deeper structure impractical as there would be four inches of foam between the concrete portions of the structure. Any joining of the foam surfaces would be useless in providing structural integrity between the concrete sections of such a wall, and any mechanical interconnection would have to bridge four inches of foam.
Wherefore, it is an object of this invention to provide an apparatus for the construction of monolithic concrete structures which comprises the use of a light weight, one-piece, thin-walled, durable plastic concrete molding block which initially provides for quick, reconfigurable, low skilled assembly, sufficient burst and interconnection strength to be free-standing without the need for bracing, and which becomes an integrated part of the structure thereby providing high shear strength and insulating properties thereto.
Wherefore, it is another object of this invention to provide for a foldable concrete molding block such that it can be collapsed to minimize the space requirements necessary for its shipping and storage.
Wherefore, it is still another object of this invention to provide for a concrete molding block which facilitates the installation of all types of facing materials.